CHAPTER V 

 VEGETABLE CYTOLOGY 



Vegetable Cytology treats of plant cells and their contents. 

 THE PLANT CELL AS THE FUNDAMENTAL UNIT 



Schleiden, in 1838, showed the cell to be the unit of plant structure. 

 The bodies of all plants are composed of one or more of these funda- 

 mental units. Each cell consists of a mass of protoplasm which 

 may or may not have a cell wall surrounding it. While most plant 

 cells contain a nucleus and some contain a number of nuclei, the 

 cells of the blue-green algae and most of the bacteria have been found 

 to lack definitely organized structures of this kind but rather con- 

 tain chromatin within their protoplasm in a more or less diffuse 

 or loosely aggregated condition. 



A TYPICAL PLANT CELL 



If we peel off a portion of the thin colorless skin or epidermis from 

 the inner concave surface of an onion bulb scale, mount in water and 

 examine under the microscope, we find it to be composed of a large 

 number of similar cells which are separated from one another by 

 means of lines, the bounding cell walls. Under high power each of 

 these cells will exhibit the following characteristics: 



An outer wall, highly refractile in nature and composed of cellulose; 

 which surrounds the living matter or protoplasm (See Fig. 29). This 

 wall is not living itself but is formed by the living matter of the cell. 

 Somewhere within the protoplasm will be noted a denser-looking 

 body. This is the nucleus. Within the nucleus will be seen one or 

 more smaller highly refractile and definitely circumscribed bodies, 

 the nucleolus or nucleoli. The protoplasm of the cell outside of the 

 nucleus is called the "cytoplasm." It will be seen to be clear and 



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